1. Searching for Extrasolar Planets at the VLT and MMT with Simultaneous Differential Imaging Searching for Extrasolar Planets at the VLT and MMT with Simultaneous Differential Imaging Eric Nielsen 1, Laird M. Close 1, Beth Biller 1, Rainer Lenzen 2, Wolfgang Brandner 2, Thomas Henning 2, Markus Hartung 3, Don McCarthy 1 1: Steward Observatory, University of Arizona 2: Max-Planck Institut fur Astronomie 3: European Southern Observatory Simultaneous Differential Imaging (SDI) is a promising technique to provide the first-ever direct images of extrasolar giant planets, and simulations based on our measured sensitivities suggest that our newly commissioned SDI devices (operating on the MMT and VLT telescopes) should have between 10% and 50% chance of detecting planets around the nearest, youngest stars in our program. By using the gas giant planet models of Burrows et al. 2003, as well as extrapolations of extrasolar planet populations from the radial velocity survey, we are able to quantitatively determine the likelihood that a planet around any of our target stars can be detected by our technique. For a 100 Myr K-dwarf at 10 pc, the SDI technique is sensitive to 4 Jupiter mass companions at 8 AU, or 2 Jupiter masses at 30 AU. Given this precision and our simulations, we expect our current SDI surveys (already underway, with 7 nights at the VLT and 2 on the MMT, having observed 23 stars to date) to begin yielding planet detections within two years, or else place very stringent constraints on the population of extrasolar planets not sampled by the radial velocity method. Fig. 1 – Titan imaged with the VLT SDI camera. Saturn’s moon Titan as viewed through our SDI device. The double-Wollaston design produces four identical beams, which are sent through filters at 1.575 (upper right), 1.600 (upper left), and 1.625 microns (lower left and right). Since the final filter is within the methane absorption band (see Fig. 2), we are able to subtract off Titan’s methane haze and produce a color image (center). Image: Hartung et al. 2004 REFERENCES Close, L.M. et al. 2004 ESO workshop on Adaptive Optics, ASP, in press. Rainer, L., Close, L.M., Brandner, W., Biller, B., Hartung, M. 2004, SPIE symp. 5492, in press. Biller, B.A., Close, L.M., Lenzen, R., Brandner, W., McCarthy, D., Nielsen, E., Hartung, M. 2004, SPIE submitted. Hartung, M., Herbst, T. M., Close, L.M., Lenzen, R., Brandner W., Marco, O., Lidman, C. 2004 A&A 421 L17-L20. Burrows, A., Sudarsky, D., Lunine, J. 2003 ApJ 596:587-596. Sudarsky, D. Private Communication. ACKNOWLEDGEMENTS We acknowledge support from NASA Origins grant NAG5-12086 and NSF SAA grant AST 0206351. This material is based upon work supported by the National Aeronautics and Space Administration through the NASA Astrobiology Institute under Cooperative Agreement No. CAN-02-OSS-02 issued through the Office of Space Science. Fig. 2 – SDI filters and theoretical young planet spectrum. Our three narrow-band filters over the theoretical spectrum of a 30 Myr, 3 M Jup planet (Sudarsky, D., private communication). The drop in flux when moving into the methane absorption band allows us to differentiate between speckles and planets. Fig. 3 – Sensitivity limits of the SDI technique. Using an SDI dataset from a 100 Myr K1 star at 10.4 pc (m H =4.1), we show our sensitivity (in units of magnitudes in our 1.575 micron filter) as a function of separation from the primary. The SDI technique brings us to the photon noise limit for our observations past 0.4” Fig. 4 – Planet hunting with standard AO. Simply combining the data from our three filters leaves numerous speckles, to the point that simulated planets cannot be seen in the image. Fig. 5 – Planet hunting with AO and SDI. By subtracting images inside and outside of the methane absorption feature, the speckles are heavily suppressed, while the 6 M Jup simulated planets are now in clear view, and are “confirmed” after a 33° telescope roll. Fig. 6 – Predicted success rate of SDI. Using the sensitivity curve from this star, the planet models of Burrows et al. 2003, and extrapolating from known exoplanet statistics, we simulate our ability to detect a companion planet, finding an expected detection rate of 13% (blue dots in the figure). The four simulated planets from Fig. 5 are plotted as green circles.